Indeed never really put the results in on the rallies. Reliability problems as well if i remmeber correctly. Read an article about the 6R4's from the guy in charge of the motorsport division at the time who said they were considering turbocharging it but obviously never had the time.

Also read ages ago that audi had a near 1000bhp prototype of the S2 in the pipeline in order to keep up with the Lancia S4 and 205 T16. the test driver apparently commented it went straight on corners no matter what you did on boost.
To think how group B would have evolved

Audi were behind on the times with there chassis design and engine layout too, which proabably didnt help.